A pointed metal wire of a diameter in a range from 12 to 50 micrometer (0.5 to two thousandths inch) is often used to contact a micron size Schottky barrier metal anode. The extreme tip of the wire must have a small radius of curvature, and certain high frequency (above 100 GHz) applications also require a given cone angle at the tip for electrical and mechanical reasons. Materials commonly used in the wires or whiskers for high frequency applications, are gold and its alloys, phosphor bronze, and tungsten. Stress relieved grade C phosphor bronze wire is especially useful as a contact whisker material for high frequency applications, because of its high mechanical strength and springiness.
One technique for forming a pointed phosphor bronze wire or whisker of the desired cone angle and extreme tip diameter or radius involves electrochemical etching in chromium trioxide. Since chromium and its compounds are extremely toxic, there is considerable need for a less objectionable pointing solution. A pointing technique which avoided the use of highly toxic mateials and which enabled the pointing of wires of controlled cone angle and extreme tip diameter, would be of considerable value.